Strange one here. I recently bought an 07 xkr,test drive and 100mile drive home was faultless,a few days later it wouldn't start.
The car is fitted with a Chinese (no name that I can read) remote controlled battery isolater. It is set up with the battery - going to a relay & from the relay to ground.
There is also a battery monitor fitted which has 4 wires coming from it. 2 go to the battery terminals, the other 2 bridge across the ground lead that goes to the relay.
I have been double locking the car and pressing the off button on the isolater fob for the few days I've had it just to see how it works really. I understand it's not a good idea to keep effectively disconnecting the battery.
Normal operation seems to be pressing the on button on the isolater fob,the indicators and sidelights (markers) flash,unlock car andpress start.
Yesterday morning I pressed the isolater fob "on" and the indicators flashed but the sidelights stayed on,I unlocked the car pressed start but the ignition didn't come on. I tried the sequence a few more times and eventually the car started. I turned it off and it wouldn't start again. Turned it off again and waited a while and it started again.
Went out for a drive and the dash was lit up like a Xmas tree, fault codes cycling on the dash,key battery low, DSC not available,DTC,a suspension warning,engine temp warning,gearbox fault which eventually went into 1stnor 2nd gear limp mode and the pedestrian system fault warning all accompanied by an annoying beeping from the dash.
I assumed it was a battery issue and bought a very expensive fully charged AGM battery, this sorted all the dash lights except the car fob low battery warning and the pedestrian system fault.
I fitted a new Duracell fob battery which got rid of the dash warning however the pedestrian system fault remained as did the beeping. The beeping only happens when the far is moving.
I disconnected the isolater entirely and bolted the battery - to it's ground. The car will unlock but is dead other than the interior lights,horn and cd player, which always goes through a cycling 8x like it's looking for a cd.
I reconnected the isolater and pressed on, unlocked the car and it started. I turned it off to try it again,the indicators flashed but the sidelights stayed on and it won't start again.
So I left it isolated again for 10 mins,pressed the isolater fob on, unlocked the car and it started, even the pedestrian fault had gone. I went for a drive, there was no pedestrian warning but the beeping when moving was still there. Interestingly there was a new apply footbrake and handbrake yellow message. I stopped the car, put it in P and with my foot on the brake applied the handbrake.
I then put it in D and pressed the gas, there was no warnings, the dash was normal with the clock in the centre and the beeping had gone.
Went home,turned the car off but left it unlocked, an hour and 45mins later the sidelights came on, I tried the start button and it was dead again, I pressed the isolater fob off and on again, the indicators and sidelights flashed and the car started.
I've got it locked with one press of the key fob at the moment just to see if anything will happen.
The relay has got a small coil of wire on the side which I assume is the antenna for the isolater fob. The relay is powered by a wire to the battery+, you would think the isolater is independent from the cars electrical system but it can't be because the indicators and sidelights are flashing.
Here are some pics that hopefully someone can make sense of.
I have ordered some impact sensors even though it was fine for the first 2 days
picture of battery monitor is with old battery readingsForgot to mention there are zero fault codes and I've checked loads of times.

 

Take off all that Chinese crap and buy a new and Fully Charged car battery. Only after that can you find out if you have a discharge problem to be dealt with, which is unlikely.

 

First rule in troubleshooting: remove all the extra stuff to make sure the basic stuff is working.

 

I know it’s a long winded post so you probably just skimmed through it but I did exactly that.

 

I saw the Disconnection, but then you stated you reconnected it...
"I disconnected the isolater entirely and bolted the battery - to it's ground. The car will unlock but is dead other than the interior lights,horn and cd player, which always goes through a cycling 8x like it's looking for a cd.
I reconnected the isolater and pressed on, unlocked the car and it started. I turned it off to try it again,the indicators flashed but the sidelights stayed on and it won't start again."
Now remove it completely, leave it off, and buy a new battery and Fully Charge it before you try again.

 

I completely disconnected it but the car will not start without it. I don’t know how the isolater fob has any control over the car but it’s doing something to immobilise it. I’m waiting for Jaguar sdd software to arrive to hopefully see if the isolater fob has been coded in. Until then I need a vehicle, even if it’s playing up.

Again, it’s a very long post but I did say I bought a brand new, fully charged battery before I disconnecting it all to see if it fixed it.

At the moment it’s been left all connected and locked with one press of the car key for 4hrs, I just unlocked it and it started right up. I’ll see if it starts in the morning.
As you are probably aware, 2 presses of the key fob shuts all the modules down and uses much less power but it seems to shut down doing that.

I’ve been experimenting with: leaving it unlocked (see result in post), now with one press of the key fob (good so far)

 

Sounds like the grounding is being interrupted somehow.

Post some wide area pics of the installation battery, battery area itself, I'm not sure where the negative cable goes as I would need to remove the left side carpet on mine:

 

Looks to me if you joined the two lugs on the black relay/switch then the battery is grounded - so technically the system is bypassed. Although you might be better unraveling that shunt arrangement with the two screws on it and connecting the battery cable to the original ground point, that way you are back to "factory" wiring.

 

Sorry, I mostly did skim the long original post. I did see most of the relevant content though.
The new battery MUST be charged to get full, as 'new' batteries are not fully charged.

 

Any idea how old the battery was when you bought the car? It may have been on it's last legs causing all the issues rather than the disconnect system. As Cee Jay said it's best to charge the battery yourself when buying a new one. Can't remember if I charged the new one I fitted back in 2016, I probably did as the forum is/was full of folks with battery issues.

 

I wasn’t sure how old and knowing how voltage sensitive these cars are I bought the best battery I could and charged it. Seems to be ok so far with just the one lock press, I’m guessing an auto electrician coded the isolater fob to the ecu thinking it was a good idea, it might “connect” with the 2nd press of the car fob or something . I’ll keep posting until I fix it, I was hoping a Jaguar electrics/coding expert might chime in as to why/how the isolater fob is controlling the indicators/sidelights and more.

 

Already done that, I’ve checked the ground connection too. I fail to see how the switch in the relay can be doing anywhere near the same job as a heavy ground cable. As I said,when I get the software I might be able to see the other fob added and remove it from the system.

 

I doubt that key fob was somehow programmed to the Jag, how the fob messes with the lights I dunno. Once you bypassed the relay/breaker the car should be back to normal. The key fob should have no effect on the car/lights once the relay/breaker is bypassed.

I'd also doubt the RF signal from that key fob is powerful enough to effect the Jag's electronics.

 

I wonder with the start problems if that shunt is acting up. Probably best to take it out altogether and remove the power to the receiver/battery display.

 

To belabor the point just a bit -- you removed the the isolator, the shunt, and the battery meter from the circuit and had the negative connected to the chassis? I ask this because there is a wire that just doesn't make any sense to me, so if any of it was left in the circuit that might be the issue.

There are several reasons the picture is confusing
1. Let's start with that red wire coming off the top stud of the mystery box. That runs back along the battery cable and appears to cross under the styrofoam piece and attach to the square strut. Aside from violating every convention of black is negative and red is positive, where the heck is it going and why?
2. Next let's look at the lead from the lower post, which should be running back to the battery, but we can't be 100% sure as it disappears under the same styrofoam piece. There's another pair of wires tapped into it, including a red one (that again should be a positive wire in any reputable wiring setup). Those two wires are taped together and lead off the bottom of the picture. Are they the same wire that comes back in from the bottom and runs off the left? What else is going on in that wide spot?
3. There's a wire running from the right to the left. As it exits the left, it looks to have a red and blue wire. The picture oof the battery monitor seems to have some blue wires on it -- is that where those two wire bundles are heading off to the left?

Not trying to be pedantic about this, it just that we can't offer much help with having the full picture of where these wires are going, and what you tried. When you disconnected, did you just take the lead off the lower stud and attach it to the chassis? Did you remove the red wire?

Like McJag222 said, getting the system back to 100% factory is important -- you have to completely clear out the tentacles of whatever that device is.

 

There are two units at play here, one is that PZEM-015 battery monitor system and the key fob battery/disconnect relay system. I'd punt the shunt.

 

I wonder if I'm being a bit OTT but I wouldn't buy any modern Jaguar which has been subjected to significant electrical modification as the electrics are the most sensitive area of the car. I went to a dealer to look at an XK8 about a year ago which had rear parking sensors. When I opened the boot and removed the floor panel I could see that the parking sensors had been retrofitted as the cabling was clearly not Jaguar. I told the salesman that it was not the car for me.

Richard

 

There's no way to modify the ECM software to add on aftermarket accessories so no worry there. As every keeps saying, bring the car 100% to original factory wiring with no modifications and work from there. And of course make certain the battery's being charged with a proper charger, not a tender or maintainer. Might need to charge for more than 1 day. Also disconnect the battery cable when doing so with only the charger connected to the battery, then when reconnecting, everything will have had a soft reset.

 

i did this too.

Thanks though.

 

So far, nobody seems to have bothered to read my post properly or they wouldn’t keep telling me to do things I’ve already done or ask me to explain what I’ve already explained. I blame myself for writing such a long post but I wanted to report everything I’d done to avoid this.
Dont get me wrong, I appreciate any replies but it’s pretty pointless everyone in the replies telling me to do exactly what I’ve done in my post.
If you think I’m being ungrateful, read my post properly and then read the replies.

I’ve been doing more research and I’m going to replace the alarm sounder as it’s batteries could be worn out and the car might keep waking up repeatedly to try and charge them, others have reported batteries losing charge overnight because of it.